In many applications, a workpiece needs to be thinned or processed with the support of a carrier to make the workpiece mechanically stable. The workpiece can be temporarily bonded to the carrier using adhesives. At end of the application, the workpiece needs to be debonded or separated from the carrier, and cleaned of any residue adhesives. For example, in semiconductor wafer thinning process, the workpiece can be a semiconductor wafer or device wafer on which thousands of chips are finally made. Widespread applications of smartphones, tablets, and portable consumer electronics are driving semiconductor packaging towards thinner, smaller, and more integrated directions. Wafer-level packaging (WLP) techniques is rapidly reducing the size of packages for easier integration into mobile electronics. The wafer thinning process used in device miniaturization and packaging has attracted more and more attention. Thin wafers offer the benefits of improved heat dissipation, three-dimensional (3D) stacking, reduced resistance, and substrate flexibility. In through silicon via (TSV) based 3D-IC wafer level packaging, wafers need to be thinned to less than 100 microns (μm). The thinning process needs to be high throughput and low cost to be suitable for volume production.
Wafer thinning is primarily achieved by mechanical grinding (back-grinding), polishing, and chemical etching. Thin wafers, especially ultra-thin wafers (thickness less than 60 microns or even 30 microns) are very unstable, and more susceptible to stress than traditional thick wafers. During processing, thin wafers may be easily broken and warped. Therefore, temporary bonding to a rigid support carrier is required. Thinned device wafers need to be supported for use on the backside in grinding process and subsequent processes such as photolithography, etching, plating, vacuum deposition, reactive ion etching, and so on.